NFSv4: Try to return the delegation immediately when marked for return on close

Add a routine to return the delegation immediately upon close of the
file if it was marked for return-on-close.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/delegation.c

@@ -639,6 +639,39 @@ int nfs4_inode_return_delegation(struct inode *inode)
 	return err;
 }
 
+/**
+ * nfs_inode_return_delegation_on_close - asynchronously return a delegation
+ * @inode: inode to process
+ *
+ * This routine is called on file close in order to determine if the
+ * inode delegation needs to be returned immediately.
+ */
+void nfs4_inode_return_delegation_on_close(struct inode *inode)
+{
+	struct nfs_delegation *delegation;
+	struct nfs_delegation *ret = NULL;
+
+	if (!inode)
+		return;
+	rcu_read_lock();
+	delegation = nfs4_get_valid_delegation(inode);
+	if (!delegation)
+		goto out;
+	if (test_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags)) {
+		spin_lock(&delegation->lock);
+		if (delegation->inode &&
+		    list_empty(&NFS_I(inode)->open_files) &&
+		    !test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
+			clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags);
+			ret = delegation;
+		}
+		spin_unlock(&delegation->lock);
+	}
+out:
+	rcu_read_unlock();
+	nfs_end_delegation_return(inode, ret, 0);
+}
+
 /**
  * nfs4_inode_make_writeable
  * @inode: pointer to inode

fs/nfs/delegation.h

@@ -42,6 +42,7 @@ int nfs_inode_set_delegation(struct inode *inode, const struct cred *cred,
 void nfs_inode_reclaim_delegation(struct inode *inode, const struct cred *cred,
 		fmode_t type, const nfs4_stateid *stateid, unsigned long pagemod_limit);
 int nfs4_inode_return_delegation(struct inode *inode);
+void nfs4_inode_return_delegation_on_close(struct inode *inode);
 int nfs_async_inode_return_delegation(struct inode *inode, const nfs4_stateid *stateid);
 void nfs_inode_evict_delegation(struct inode *inode);
 

fs/nfs/nfs4state.c

@@ -766,6 +766,7 @@ void nfs4_put_open_state(struct nfs4_state *state)
 	list_del(&state->open_states);
 	spin_unlock(&inode->i_lock);
 	spin_unlock(&owner->so_lock);
+	nfs4_inode_return_delegation_on_close(inode);
 	iput(inode);
 	nfs4_free_open_state(state);
 	nfs4_put_state_owner(owner);